(a) Field of the Invention
The present invention relates to a chemical-mechanical polishing apparatus, more in detail to the chemical-mechanical polishing apparatus which can perform polishing a wafer at a stabilized amount by sufficiently controlling the polished amount of the wafer.
(b) Description of the Related Art
In manufacture of a semiconductor device, a wafer is polished by employing a chemical-mechanical polishing apparatus (hereinafter referred to as xe2x80x9cCMP apparatusxe2x80x9d). It is important to keep the polished amount in a fixed range when the polishing is conducted by employing the CMP apparatus. The CMP apparatus generally has a controller for controlling the length of polishing time.
An example of a conventional CMP apparatus will be described referring to FIG. 1.
The conventional CMP apparatus 10 has a polishing block 12 for polishing a film formed on a wafer and a controller 14 for controlling the length of polishing time.
The polishing block 12 includes a polishing treatment section 15 for polishing the film on the wafer, a thickness meter 16 for measuring film thicknesses before and after the polishing and a conditioning treatment section 18 having a dresser for setting a polishing pad. The polishing treatment section 15 includes the polishing pad (not shown), a polishing table (not shown) which rotates while holding the polishing pad, a wafer holder (not shown) which rotates the film while pressing the film on the wafers to the polishing pad, and a time section (not shown) for measuring a length of polishing time.
The controller 14 includes a thickness data input section 21 for receiving film thickness data transmitted from the polishing block 12, a rate calculation section 22 for calculating a polishing rate from the film thicknesses before and after the polishing and the length of the polishing time, a time calculation section 23 for calculating the length of polishing time for the next wafer, and an output section 24 for transmitting the calculated length of polishing time to the polishing block 12.
In order to polish the film on the wafer by employing the conventional CMP apparatus 10, at first, the film thickness before the polishing is measured by the thickness meter 16 for measuring the film thicknesses, and the data obtained by this measurement (hereinafter referred to as xe2x80x9cpre-polishing thickness dataxe2x80x9d) is sent to the controller 14.
Then, a polishing treatment is performed. The CMP apparatus 10 conducts a setting treatment upon the completion of the polishing.
Further, the film thickness after the polishing is measured by employing the thickness meter 16, and the data obtained by this measurement (hereinafter referred to as xe2x80x9cpost-polishing thickness dataxe2x80x9d) is sent to the controller 14. The controller 14 calculates a current polished amount based on the pre-polishing thickness data and the post-polishing thickness data, and also calculates the length of time required for the polishing treatment of the next wafer, and the length of time thus obtained is sent to the polishing block 12.
However, in the conventional CMP apparatus, the length of the polishing time is always varied because the conditions for setting the polishing pad are not constant. The required length of the polishing time for a single wafer increases with every wafer polishing and the length of the polishing time is considerably reduced immediately after the setting of the polishing pad. Therefore, disadvantages have been recognized such that the polished amount of the wafer cannot be sufficiently controlled and the polishing pad is liable to be damaged and has a reduced life.
In view of the foregoing, an object of the present invention is to provide a CMP apparatus which sufficiently controls a polished amount of a wafer and conducts a stable polishing treatment.
The present invention provides a CMP apparatus comprising: a polishing pad; a polishing table rotatable while holding said polishing pad; a wafer holder which presses a film on a wafer to said polishing pad while holding the wafer; a dresser for setting said polishing pad each time after a specified number of said wafers are chemically and mechanically polished; and a conditioning controller including a rate calculation section for calculating a polishing rate and an establishing section for establishing conditions for setting said polishing pad based on the calculated polishing rate.
In accordance with the CMP apparatus of the present invention, after polishing of the specified number of the wafers, the setting conditions of the polishing pad can be suitably corrected or the conditions of the polishing pad can be maintained nearly constant, and the polishing can be properly conducted. Accordingly, the CMP apparatus can be provided in which the polishing rate is stabilized and the polished amount is sufficiently controlled. Further, the damages generated on the polishing pad are much smaller than those of the prior art. In the present invention, it is preferable that the specified number of wafers be generally 1 or 2.
The above and other objects, features and advantages of the present invention will be more apparent from the following description.